The aim of this investigation is to advance the understanding of the proliferative behavior of normal and neoplastic hematopoietic cells, by developing new and improved mathematical models of their growth and development. In close collaboration with Dr. B.D. Clarkson and his co-workers at Sloan-Kettering Institute, we have commenced and/or will pursue investigations in the following directions. We shall continue our investigations into the fundamental kinetic behavior of cell populations, with especial regard to the existence and properties of the Go state. We are examining quantitatively the proliferative and differentiation capacities of human blood cells, as revelaed by observations of clones of granulocyte-macrophage colony-forming cells. We are continuing the development of a theory of cell populations to represent temporal changes in DNA histograms obtained by FMF observations.